Quantifying of plant species diversity , composition and density at Dammam Region , Eastern province , Saudi Arabia

This study assessed the diversity composition and density of plant species at Dammam Region, Eastern Province, Saudi Arabia. Plant diversity is a vital component of any ecosystem. It is a wellknown fact that, worldwide, thousands of plant species are endangered and facing extinction with the current trend of their influence and destruction. Changes in the structure of the assortment of resources lessen plant community’s opportunity to respond to new problems and occasions. Plant diversity is facing danger of new plant diseases or pests, species extinction, climatic changes and other obstructions. A survey of 12 different sites was done and botanic biodiversity was evaluated. The plant diversity was evaluated by applying different methods namely: relative abundance index, species richness D* index and Shannon-Weaver index. It is clear that many plant species and habitats of Dammam area are subjected to severe disturbance due to new constructions without environmental impact assessment.


INTRODUCTION
In the last three decades, there is a massive development in construction and industrial activities at Saudi Arabia.More or less parallel to national development, there is a growing awareness concerning the impact of temperature rise, industrialization, desertification and shift in the growing seasons of plants, loss of pollinators and seed dispersers, and increasing frequency of forceful weather events such as drought, storms and floods, making several valuable plants to be extinct (Bapat et al., 2012;Gardener et al., 2009).According to the International Union of Conservation of Nature (IUCN 1980), it is estimated that the current species extinction rate is between 1000 and 10,000 times higher than it would naturally be.It is acknowledged that the future survival of humanity depends on the conservation and protection of natural wealth, and destruction of a species or a genetic line symbolizes the loss of a unique resource.This type of genetic and *Corresponding author.E-mail: saa14@fayoum.edu.eg.
Creative Commons Attribution the Author(s) agree that this article remains permanently open access under the terms of License 4.0 International License environmental deprivation is irreversible (Poi, 2011).The single most important botanical task in eco-civilization construction is the conservation of plant species with their genetic diversity (Hamilton et al., 2017).The environmental factors affect the plant species composition and the establishment and stability of seedlings.Furthermore, the interactions of environmental factors are important in the restoration process and must be considered in the management of the areas (Gattie et al., 2003).
In fact, there is no doubt that plants grow naturally in different environments and are exposed in these environments with a range of climatic factors that suit their growth and sometimes exceed conditions that are not commensurate with their requirements for growth.Soil types with different structure and nutrients are important for plant growth and community development.Although, 95% of experimental studies support a positive relationship between diversity and ecosystem functioning, many have found that only 20 to 25% of species are needed to maintain most biogeographically ecosystem processes (Schwartz et al., 2000).Rahman et al. (2004) investigated the medicinal plant diversity in the flora of the Kingdom of Saudi Arabia; this communication emphasizes the importance of setting up conservation priorities, and sustained development of various medicinal plants of Saudi Arabia.Saudi Arabia has a hot desert climate and rainfall is scarce in most parts of the country.The diversity of the flora of Saudi Arabia as well as other countries in the peninsula has received less attention for a long time due to its arid climate.The climatic and anthropogenic factors are the most vital factors affecting plant species distribution and abundance (Emad and El-Ghazali, 2013;Kaky andGilbert, 2016, El-Shabasy, 2016).
In the current study, different measures of plant diversity are introduced with an effective indicator of underlying feature diversity.Phylogenetic diversity will be viewed based on cladistics relation among any group of taxa, not just species (Faith, 1992;Alfarhan, 1999).
Regarding conservation priorities, the measurements developed in the present study was initially intended for application on species, population and ecosystem levels.However, since it is not an easy task, the study of plant diversity with time over specific place is highly required.The purpose of the present study is to shed light on assessment of plant species diversity, composition and density at Dammam Region, Eastern province of Saudi Arabia.Plant resources are a vital measure of a country's wealth.
Its unsustainable use can lead to irreversible/permanent destruction to the ecosystems.

Study area
This study is conducted at Dammam city and varsities with an area of about 800 km 2 .Dammam is a city found in Eastern Province, Saudi Arabia.It is located at 26.43° Latitude and 50.10°Longitude and it is situated at elevation of 10 m above sea level.The studied site is illustrated in Figure 1.Geomorphologically, Dammam Region is characterized by its low surface with gradual elevation towards north and lake of Wadies.It lies within the Central coastal lowland subregion of Eastern costal region.
Climatically, the study area is classified as an arid to extremely arid region (UNESCO, 1977).The mean annual rainfall is 6.6 mm.The dominant temperature fluctuates between mean minimum of 10.2°C and mean maximum of 44.6°C.

Collection of data
Several field trips were done in and 12 sites were investigated (Tables 2 and 3).In each site, the plant species are listed by evaluating several parameters.The collected plant specimens were identified and named according to Mandaville (1990), Migahaid (1996) and Chaudhary (1999Chaudhary ( , 2000Chaudhary ( , 2001)).Calculations of various vegetative parameters are according to Magurran (2003).

Field study
In addition to determination of the community type, plant covers, number of individuals per m 2 for each species, also, phenology and soil feature are recognized.All sites were documented with different photos and by GPS.Samples of obscure plant species were collected, pressed and preserved on paper sheets for full identification.Some soil samples were collected to compare habitat features of plants common in different localities.Twelve soil samples were collected, covering different plant communities and habitats.
Field visits were repeated to the study area to investigate communities and plant species and make the following measurements: 1.A list of the plants "with complete scientific identification", with a case study of each species, growth aspects and phonological features.2. Species richness of the vegetation in studied sites were calculated as the average number of species per stand, and species index D* turn-over as the ratio between the total number of species in the sample (N) and the number of species (S): Species richness index D* = (S -1)/Log N 3. Relative abundance index" Ra" was calculated; Ra = N × 100/N, where N is the number of a species and Ns is the total numbers of all individuals.The results are categorized according the following scale: Dominant species = >70%, abundant spp.= 40 to 70%, frequent = 10 to 40% and rare spp.= >10% 4. Relative evenness "H" of species are calculated using Shannon-Weaver (Pielou, 1975), on the basis of the relative cover of species.

Soil analysis
Soil samples were collected at 3 random points from each site as a profile (composite samples) from two depths: surface layer 0-5cm and active absorbing layer 5-30cm depth.Soluble chlorides were determined by precipitation by AgCl and titration, also, sulphates and ammonia (ppm) were precipitated gravimetrically and estimated according to A.O. A.C (1998).Major cations such as sodium, potassium, calcium and magnesium are determined in the 1:5 soil extract by flame photometer (Jones, 2001) and their concentrations are expressed in mg kg -1 dry soil.
Data in Table 1 indicates that soils supporting the growth of vegetation at study area are rich in calcium (68330 mg/kg) at site 8, sodium (49710 mg/kg) at site 2 and magnesium (8960 mg/kg) at site 8. Ammonia and chloride are commonly low in the studied area except site 3 where it reached 79682.33 ppm in surface soil layer.
The soil samples from sites 11 and 12 (Figure 1) have very low level of element contents.Some species are subjected to extensive decrease, over grazing and/or over collection (  7).

Species diversity
The Shannon-Wiener's diversity index ranging from 2.815 to 0.588 are recorded for sites 6 and 7, respectively (Table 3).Relative abundance values for each site show that majority of the investigated species are within the rare category with one dominant species (Table 3).Figures 7 and 8 illustrate number of families and species in the study area.

DISCUSSION
Climate change is a crucial factor to consider when assessing the health of any species' population, but conservationists are left with the challenge of deciding exactly how to measure its potential impact on a given species (Still et al., 2015).It is worth mentioning that the vegetation is subjected to severe arid conditions, with prevalent climatic conditions in the area.Soil analysis (Table 1) illustrate wide diverse of chemical composition of soils supporting the growth of prevailing species of the study area.
Table 2 illustrates that the dominance and abundance of plant species varies widely.The existing species can be classified into different categories: Folk industries plants, medicinal plants, fodders/grazing plants and edible/food plants.Moreover, the results of species relations and soil factors revealed the fact that different species have reacted to soil differently.
The vegetation in the study area is the desert shrub rangelands type (Rahman et al., 2004).
A floristic analysis shows that majority of plants in the study area are annuals, while the minority group is in the tree (Figures 7 and 8).The dominance of members of Asteraceae and Chenopodiaceae, followed by Poaceae and Zygophyllaceae coincides with the findings of authors such as Turki and Al-Olayan (2003), El-Ghanim et al. (2010) and Alatar et al. (2012).On the other hand, the rainy season provides better chance for the appearance of a considerable number of annuals, which give a characteristic physiognomy to their vegetation (Shaltout and Mady, 1996;Hosni and Hegazy, 1996;Shaltout et al., 2010;Alatar et al., 2012).Moreover, the life form spectrum in eastern part of the study area reflects a typical desert flora, the majority of species being therophytes and chamaephytes.These results agree with the spectra of vegetation in desert habitats in other parts of Saudi Arabia This indicates that the dominance evenness of species generally tend to be within low values indicating low diversity.Degradation of the rangeland is evident in many parts of Saudi Arabia as a result of a long history of overgrazing (camels and sheep are the main grazing animals), overcutting, and many social, economic and cultural factors (Miller and Nyberg, 1991;Schultz and Whitney, 1986;Al-Rowaily et al., 2015).Protection against overexploitation provides a chance for regeneration of vegetation and for improvement of phytomass levels (Thomas et al., 2017).This is emphasized by many investigators (Gilbert, 2011;Pan et al., 2012;Chafjiri et al., 2016).
Generally, the plant diversity in the study area is extremely important from the environmental point of view as well as the economic importance.The environmental value is represented by: sand dune fixation, wind breaks, phytoremediation, atmospheric filtration and ecological balance, etc. (Meshal et al., 1985;Al-Taisan, 2009;Adler, 2011).Individual ecosystem functions generally show a positive asymptotic relationship with increasing biodiversity, suggesting that some species are redundant (Hector and Bagchi, 2007).
The diversity measurements (Table 3) illustrate low diversity of vegetation in the most studied sits.The plant diversity in Dammam sharply needs intensive conservation program, integrated studies and contentious monitoring.To overcome these hurdles, there is a need for coordinated efforts of scientists, government departments and nongovernmental organizations to undertake effective strategies for conservation of plants at Dammam area.This is emphasized by Shaltout et al. (1996).They found that 14 years of protection against grazing and human impacts of the coastal lowland vegetation in Eastern Saudi Arabia has led to an increase of 68% in the total cover, 33% in species richness and 32% in species relative evenness.Many of the species with significantly higher abundance in the protected area are important forage and/or fuel plants.

Conclusion
The study revealed that the high plant diversity and distribution of many plant species are deteriorated in Dammam due overgrazing and social behavior.Therefore, the plant diversity in Dammam sharply needs intensive conservation program, integrated studies and contentious monitoring.To overcome these hurdles, there is a need for coordinated efforts of scientists, government departments and non-governmental organizations to undertake effective strategies for conservation of plants at Dammam area.

Figure 1 .
Figure 1.(A) Map of the study area illustrating the sampling sites.(B) Satellite map of Arabian Gulf, Saudi Arabia, showing the study areas.

Figure 5 .
Figure 5. Photo showing low diversity among site dominated with Zygophyllum coccinum.

Figure 7 .
Figure 7. Number of families and species in the study area.

Figure 8 .
Figure 8. Growth of relative spectrum of the study area.

Table 1 .
Some chemical features of the soil supporting the growth of studied vegetation in different sites of Dammam area.

Table 2 .
Endangered species recorded in the study area.

Table 3 .
Relative abundance, species richness index D* and Shannon-Weaver index of plant species grown in the studied area at Dammam.